1. Field of the Invention
The present invention relates to a radiation detection device; and, in particular, to a radiation detection device having a light-receiving portion with a large area, which is used for medical X-raying and the like.
2. Related Background Art
While X-ray sensitive films have conventionally been used for medical and industrial X-raying, radiation imaging systems using a radiation detection device are becoming pervasive due to their convenience and the storability of their photographed results. Such a radiation imaging system uses a radiation detection device having a plurality of pixels so as to acquire, as an electric signal, two-dimensional image data formed by a radiation, and processes thus obtained signal with a processing unit, so as to display it on a monitor. A typical radiation detection device is configured such that a scintillator is disposed on one- or two-dimensionally arranged photodetectors so as to convert the incident radiation into light, which is then detected.
CsI, a typical scintillator material, is a hygroscopic material which dissolves by absorbing vapor (moisture) in the air. As a result, characteristics of the scintillator, such as resolution in particular, have disadvantageously deteriorated.
Known as a radiation detection device having a structure for protecting the scintillator against moisture is the technique disclosed in Japanese Patent Application Laid-Open No. 5-196742. In this technique, a water-impermeable moisture-proof barrier is formed on the upper side of the scintillator layer, thereby protecting the scintillator against moisture.
In the above-mentioned technique, however, it is hard for the moisture-proof barrier in the outer peripheral portion of the scintillator layer to come into close contact with the substrate of the radiation detection device. In particular, in a radiation detection device having a large area used for chest X-raying or the like, due to its long outer peripheral portion, there is a fear of peeling off the moisture-proof barrier. Hence, the hermetic sealing of the scintillator layer might become incomplete, moisture penetrates into the scintillator layer, it might cause a problem that deteriorates characteristics of the scintillator layer.
Also, the above-mentioned technique discloses a method of making a moisture seal layer for the moisture-proof barrier in which a silicone potting material or the like is coated on the scintillator layer in a liquid state or coated inside a window member disposed on the light-receiving surface side of the radiation detection device and then the window member is disposed on the scintillator layer before the moisture seal layer is dried, thereby fixing the moisture seal layer. In this method, it is hard to uniformly form the moisture seal layer on a scintillator layer having an irregular surface form, whereby adhesion may deteriorate. This phenomenon tends to occur in radiation detection devices having a large area, in particular.
In view of the foregoing problems, it is an object of the present invention to provide a radiation detection device having a uniform protective film, which is easy to make, for protecting the scintillator against moisture; and a method of making the same.
In order to achieve this object, the radiation detection device of the present invention comprises: (1) a light-receiving device array in which a plurality of light-receiving devices are one- or two-dimensionally arranged on a substrate; (2) a scintillator layer deposited on said light-receiving devices and provided with columnar crystals; (3) an organic film formed over the top and side surfaces of the scintillator layer and the substrate surface around the scintillator layer and intruding into gaps among the top part of said columnar crystals to cover the scintillator layer.
As a consequence, the incident radiation is converted into detectable light with the light-receiving device by the scintillator layer. As the resulting light image is detected by the one- or two-dimensionally arranged light-receiving devices, an electric signal corresponding to the incident radiation image is obtained. The scintillator layer has a characteristic of deteriorating by absorbing moisture. In the present invention, however, since the scintillator layer is covered with the organic film, and this film intrudes into gaps among the top part of the scintillator layer, the scintillator layer is completely hermetically sealed so as to be isolated from the external atmosphere, thus being protected against vapor in the air.
This organic film may be preferably fixed to the substrate around the scintillator layer. Thereby the organic film securely fixed to the substrate and hermetically sealed the scintillator layer.
The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only and are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description.